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How to increase soybean profits by $100 per acre (for free)

If you're battling soybean cyst nematode (SCN), there's an easy way to pump your profits by up to $100 per acre this year.

Match up a high-yielding SCN-resistant variety with the type of nematode in your field.

Sounds simple, doesn't it?

Terry Niblack, University of Illinois (U of I) Extension nematologist, says increased profits ranging from $85 to $115 per acre resulted in U of I trials when high-yielding resistant varieties matched to the SCN population in the field were compared to low-yielding, highly SCN-resistant varieties unmatched to a particular SCN population.

Yet, doing so requires you to rethink SCN. Here's how.

Acknowledge you likely have SCN
If you farm in the South or the Corn Belt, it's likely SCN infests your soybean fields. For example, a 2005 U of I survey found 84% of that state's soybean acreage was SCN-infested.

This was on par with a 1995-1996 SCN Midwest survey that found the following infested soybean acreages in these states:

  • Minnesota: 54%
  • Iowa: 74%
  • Missouri: 71%
  • Illinois: 83%
  • Indiana: 47%
  • Ohio: 60%

Yet, SCN doesn't register on the radar of many farmers. A recent seed dealer survey conducted by the U of I showed just 48% of Illinois farmers grow SCN-resistant varieties -- a key way to deal with the problem. Meanwhile, a 2005 Purdue University survey showed 62% of surveyed Indiana farmers indicated they had no problems with SCN.

Lack of visual symptoms likely plays a role in this line of thinking. "You can have a 30% yield loss without seeing anything," says Niblack. "A lot of people get upset about SDS (Sudden Death Syndrome) because of all the horrible symptoms, but SCN is responsible for more yield loss than SDS."

Plant resistant varieties
Along with rotating soybeans with non-host crops, planting a resistant variety is a great way to fight SCN. However, some farmers still hesitate due to yield drag concerns.

Yield drag may exist when farmers plant SCN-resistant varieties on noninfested soils. However, yield drag quickly dissolves as SCN populations increase. Both conventional and glyphosate-tolerant resistant varieties outyielded SCN-susceptible ones from four to 17 bushels per acre in 2006 Iowa State University (ISU) trials. What's more, this yield bump often occurs for free.

"Most seed companies do not charge a higher price for seed of SCN-resistant varieties," says Greg Tylka, ISU Extension plant pathologist.

Be a typist, not a racist
Seed companies have traditionally classified SCN-resistant varieties according to race. In other species -- humans included -- race works well in classifying physical differences between populations. However, it doesn't cut it with SCN populations, since there is no way to distinguish individual SCN as members of one race or another, says Niblack.

That's why a new national type system is replacing the old race system to take the guesswork out of whether a variety truly resists SCN. The HG Type test extracts SCN from soil samples in the given field. Then it tests the nematode's ability to attack the following genetic lines of SCN resistance:

  • PI 54802 (Peking)
  • PI 88788
  • PI 90763
  • PI 437654
  • PI 209332
  • PI 89772
  • PI 548316 (Cloud)

Illinois offers a condensed SCN type test for just three lines: Peking, PI 88788 and PI 437654.

This test reflects the fact that these three genetic lines form the resistance source for most soybean varieties. In Illinois, for example, these three lines make up 99% of the SCN-resistance source of varieties.

Illinois farmers can go to the Varietal Information Program for Soybeans (VIPS) brochure (www.vipsoybeans.org) and look under the SCN resistance column for the resistance source and the levels of resistance in each variety. Farmers then may match the resistance source against the nematode type in their field that the soil test has detected.

For example, a type one nematode attacks varieties with a Peking source of resistance, while a type two nematode attacks PI 88788. It's possible to have an SCN type in a field that attacks two or more sources of resistance. If SCN attacks varieties with Peking and PI 88788 resistance sources, the SCN type is 1.2.

Tylka points out that ISU SCN-resistant soybean variety trial results from 1996 to 2006 can be found at www.isuscnvarietytrials.info.

Not all the same
Not all SCN resistance is equal. In 2006 U of I trials, the top 10 SCN-resistant varieties outyielded the 10 susceptible ones in every case.

"However, average resistant varieties don't always outyield the average suspectible varieties," says Niblack. "Resistance is not created equal. There are still a lot of bad resistant varieties out there. Just because two varieties come from the same source doesn't mean there aren’t differences in genetics."

Despite the challenges, Niblack believes resistant varieties are are still the best means to fight SCN.

U of I trials in 2006 with 685 entries at 13 locations showed on average, yields increase four percent just if growers pick a resistant variety. However, that gap widens to 12% when the top 10 resistant varieties are selected according to yield potential. And when resistant varieties are matched according to the type of nematode population in the field, the yield gap jumps to 22%.

"You just need to pick the best yielding variety that matches up to the types of nematodes you have in the field," says Niblack.

If you're battling soybean cyst nematode (SCN), there's an easy way to pump your profits by up to $100 per acre this year.

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